Calibration of an imaging device can significantly improve color accuracy of images rendered by the device. For example, imaging devices such as cathode ray tubes, liquid crystal displays, plasma displays, and various printing devices, are often calibrated to determine adjustments that can be applied to either color input or drive data applied to the device. In either case, the adjusted data can then be used to control the imaging device such that the ultimate rendition of the image has improved color accuracy. Calibration can be used to account for drift in the imaging device to improve color accuracy.
For example, the calibration of a cathode ray tube (CRT) may involve attaching a measurement device, such as a colorimeter, to the display screen to measure color output of the CRT. The measured output can then be compared to analytical expected color values to determine the color errors. The determined errors can then be used to modify a lookup table (LUT) in a video card associated with a host computer so that input color data can be converted in a manner that adjusts for the determined errors. The effectiveness and accuracy of the calibration process can substantially impact color accuracy.
Precise color accuracy is particularly important for color intensive applications such as soft proofing. Soft proofing refers to a proofing process that makes use of a display device rather than a printed hard copy. Traditionally, color proofing techniques have relied on hard copy proofing, where proofs are printed and inspected in order to ensure that the images and colors on the print media look visually correct. For instance, color characteristics can be adjusted and successive hard copy prints can be examined in a hard proofing process. After determining that a particular proof is acceptable, the color characteristics used to make the acceptable proof can be reused to mass-produce, e.g., on a printing press, large quantities of print media that look visually equivalent to the acceptable proof.
Soft proofing is desirable for many reasons. For instance, soft proofing can eliminate or reduce the need to print hard copies on media during the proofing process. Moreover, soft proofing may allow multiple proofing specialists to proof color images from remote locations simply by looking at display devices. With soft proofing, there is no need to print and deliver hard copy proofs to remote reviewers. Thus, soft proofing can be faster and more convenient than hard copy proofing. Moreover, soft proofing can reduce the cost of the proofing process. For these and other reasons, soft proofing is highly desirable. The ability to achieve precise calibration of soft proofing display devices is an important factor to achieving an effective soft proofing system.